1. Field of the Invention
The present invention relates to a radiographic system for repetitiously recording and reading radiation images on image recording mediums such as stimulable phosphor sheets while they are being circulated through an image recording device, an image reading device, and a remaining image erasing device by a feed system, and more particularly to a power supply circuit breaker for breaking the power supply circuit of the radiographic system in response to a power supply interrupting command after the stimulable phosphor sheets have been placed in an optimum condition.
2. Prior Art
There are known radiographic systems which record radiation image information in stimulable phosphor sheets. The stimulable phosphor sheet is a sheet having a layer of stimulable phosphor. The stimulable phosphor is a phosphorous material which, when exposed to radiation such as X-rays, .alpha.-rays, .beta.-rays, .gamma.-rays, cathode rays, or ultraviolet rays, stores a part of the energy of the radiation. When the phosphor exposed to the radiation is subsequently exposed to stimulating rays such as visible light, the phosphor emits light in proportion to the stored energy of the radiation.
In various proposed radiation image information recording and reading systems employing stimulable phosphor sheets, the radiation image information of an object such as a human body is recorded in a stimulable phosphor sheet, the stimulable phosphor sheet is then scanned with stimulating rays of light to emit light representing the recorded radiation image information, and then the emitted light is photoelectrically read to produce an image signal which is subsequently processed to produce a radiation image that can be used for suitable purpose such as medical diagnosis (see Japanese Laid-Open Patent Publication Nos. 55(1980)-12429, 56(1981)-11395, 55(1980)-163472, 56(1981)-104645, and 55(1980)-116340, for example). In such a system, a final image may be reproduced as a visible image on a hard copy or displayed as a visible image on a CRT. In the radiation image information recording and reading systems, the stimulable phosphor sheet does not serve as a final image information recording medium, but as an image storage medium for temporarily storing image information which is to be retrieved as a visible image on a final image information recording medium. Therefore, the stimulable phosphor sheet may be repetitiously used and, preferably, should be so used for economic reasons.
A radiation image information recording and reading system employing stimulable phosphor sheets may be mounted on a mobile station such as a mobile X-ray radiographic vehicle, and the mobile station may be sent to different places for taking X-ray images of the bodies of people in groups for diagnostic purpose. In such an application, it is not convenient to carry a number of stimulable phosphor sheets on the mobile station, and the number of stimulable phosphor sheets that can be carried on the mobile station is limited. Repetitious use of a limited number of stimulable phosphor sheets in a radiation image information recording and reading system on such a mobile station is therefore practically advantageous for taking X-ray body images of many people. Such X-ray images can be taken successively at a high speed through repetitious use of stimulable phosphor sheets.
In order to make a used stimulable phosphor sheet ready and available for recording radiation image information again, radiation energy remaining in the stimulable phosphor sheet after light representing previously recorded radiation image information has been emitted and read has to be discharged or erased upon exposure to erasing light rays, in the manner disclosed in Japanese Laid-Open Patent Publication Nos. 56(1981)-11392 and 56(1981)-12599.
The inventor of the present invention has proposed a built-in-type radiation image information recording and reading system which comprises a circulatory feed means for feeding a stimulable phosphor sheet, which can record a radiation image, along a circulatory path, an image recording device in the circulatory path for applying radiation which bears image information to the stimulable phosphor sheet to record radiation image information in the stimulable phosphor sheet, a stimulating light source in the circulatory path for emitting stimulating light rays to scan the stimulable phosphor sheet with the radiation image information recorded therein, an image reading device having a photoelectric transducer for reading light emitted from the stimulable phosphor sheet upon exposure to the stimulating light rays and producing an image signal from the read light, and a remaining image erasing device in the circulatory path for discharging radiation energy remaining on the stimulable phosphor sheet after the recorded radiation image information has been read in the image reading device and before another radiation image is recorded in the stimulable phosphor sheet in the image recording device, the devices being incorporated in a singe housing of the system. The stimulable phosphor sheet is circulated through the devices for repetitious use. The proposed radiation image information recording and reading system is disclosed in Japanese Laid-Open Patent Publication Nos. 59(1984)-192240 and 60(1985)-176032, for example.
Some radiation image information recording and reading systems of the type described above have curved circulatory paths for stimulable phosphor sheets in order to achieve a smaller system size or a desired outer profile.
If the power supply circuit of the radiation image information recording and reading system is broken or opened while a stimulable phosphor sheet is being fed along a curved portion of the circulatory path, then the stimulable phosphor sheet stops in the curved circulatory path portion. When this happens, the stimulable phosphor sheet held in the curved circulatory path portion tends to be damaged or deformed as it is subject to undue bending stresses from the curved circulatory path portion. Other stimulable phosphor sheets, which may happen to be present in the image recording and reading devices when the power supply is interrupted, are also liable to suffer problems since any processing on those stimulable phosphor sheets is interrupted undesirably.